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Gas kinematics on giant molecular cloud scales in M51 with PAWS : cloud stabilization through dynamical pressure

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Abstract
We use the high spatial and spectral resolution of the PAWS CO(1-0) survey of the inner 9 kpc of the iconic spiral galaxy M51 to examine the effects of gas streaming motions on the star-forming properties of individual giant molecular clouds (GMCs). We compare our view of gas flows in M51-which arise due to departures from axisymmetry in the gravitational potential (i.e., the nuclear bar and spiral arms)-with the global pattern of star formation as traced by Ha and 24 mu m emission. We find that the dynamical environment of GMCs strongly affects their ability to form stars, in the sense that GMCs situated in regions with large streaming motions can be stabilized, while similarly massive GMCs in regions without streaming go on to efficiently form stars. We argue that this is the result of reduced surface pressure felt by clouds embedded in an ambient medium undergoing large streaming motions, which prevent collapse. Indeed, the variation in gas depletion time expected based on the observed streaming motions throughout the disk of M51 quantitatively agrees with the variation in the observed gas depletion time scale. The example of M51 shows that streaming motions, triggered by gravitational instabilities in the form of bars and spiral arms, can alter the star formation law; this can explain the variation in gas depletion time among galaxies with different masses and morphologies. In particular, we can explain the long gas depletion times in spiral galaxies compared with dwarf galaxies and starbursts. We suggest that adding a dynamical pressure term to the canonical free-fall time produces a single star formation law that can be applied to all star-forming regions and galaxies across cosmic time.
Keywords
STAR-FORMATION LAW, (CO)-C-12 2-1 MAP, NEARBY GALAXIES, SPIRAL GALAXIES, MILKY-WAY, FORMATION EFFICIENCY, INTERSTELLAR-MEDIUM, DISK GALAXIES, GRAVITATIONAL STABILITY, SUPERCLOUD FORMATION, galaxies: individual (M51), galaxies: ISM, galaxies: star formation, ISM: kinematics and dynamics

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Citation

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MLA
van der Wel, Sharon Meidt, et al. “Gas Kinematics on Giant Molecular Cloud Scales in M51 with PAWS : Cloud Stabilization through Dynamical Pressure.” ASTROPHYSICAL JOURNAL, vol. 779, no. 1, 2013.
APA
van der Wel, S. M., Schinnerer, E., Garcia-Burillo, S., Hughes, A., Colombo, D., Pety, J., … Thompson, T. A. (2013). Gas kinematics on giant molecular cloud scales in M51 with PAWS : cloud stabilization through dynamical pressure. ASTROPHYSICAL JOURNAL, 779(1).
Chicago author-date
Wel, Sharon Meidt van der, Eva Schinnerer, Santiago Garcia-Burillo, Annie Hughes, Dario Colombo, Jerome Pety, Clare L Dobbs, et al. 2013. “Gas Kinematics on Giant Molecular Cloud Scales in M51 with PAWS : Cloud Stabilization through Dynamical Pressure.” ASTROPHYSICAL JOURNAL 779 (1).
Chicago author-date (all authors)
van der Wel, Sharon Meidt, Eva Schinnerer, Santiago Garcia-Burillo, Annie Hughes, Dario Colombo, Jerome Pety, Clare L Dobbs, Karl F Schuster, Carsten Kramer, Adam K Leroy, Galle Dumas, and Todd A Thompson. 2013. “Gas Kinematics on Giant Molecular Cloud Scales in M51 with PAWS : Cloud Stabilization through Dynamical Pressure.” ASTROPHYSICAL JOURNAL 779 (1).
Vancouver
1.
van der Wel SM, Schinnerer E, Garcia-Burillo S, Hughes A, Colombo D, Pety J, et al. Gas kinematics on giant molecular cloud scales in M51 with PAWS : cloud stabilization through dynamical pressure. ASTROPHYSICAL JOURNAL. 2013;779(1).
IEEE
[1]
S. M. van der Wel et al., “Gas kinematics on giant molecular cloud scales in M51 with PAWS : cloud stabilization through dynamical pressure,” ASTROPHYSICAL JOURNAL, vol. 779, no. 1, 2013.
@article{8622318,
  abstract     = {We use the high spatial and spectral resolution of the PAWS CO(1-0) survey of the inner 9 kpc of the iconic spiral galaxy M51 to examine the effects of gas streaming motions on the star-forming properties of individual giant molecular clouds (GMCs). We compare our view of gas flows in M51-which arise due to departures from axisymmetry in the gravitational potential (i.e., the nuclear bar and spiral arms)-with the global pattern of star formation as traced by Ha and 24 mu m emission. We find that the dynamical environment of GMCs strongly affects their ability to form stars, in the sense that GMCs situated in regions with large streaming motions can be stabilized, while similarly massive GMCs in regions without streaming go on to efficiently form stars. We argue that this is the result of reduced surface pressure felt by clouds embedded in an ambient medium undergoing large streaming motions, which prevent collapse. Indeed, the variation in gas depletion time expected based on the observed streaming motions throughout the disk of M51 quantitatively agrees with the variation in the observed gas depletion time scale. The example of M51 shows that streaming motions, triggered by gravitational instabilities in the form of bars and spiral arms, can alter the star formation law; this can explain the variation in gas depletion time among galaxies with different masses and morphologies. In particular, we can explain the long gas depletion times in spiral galaxies compared with dwarf galaxies and starbursts. We suggest that adding a dynamical pressure term to the canonical free-fall time produces a single star formation law that can be applied to all star-forming regions and galaxies across cosmic time.},
  articleno    = {45},
  author       = {van der Wel, Sharon Meidt and Schinnerer, Eva and Garcia-Burillo, Santiago and Hughes, Annie and Colombo, Dario and Pety, Jerome and Dobbs, Clare L and Schuster, Karl F and Kramer, Carsten and Leroy, Adam K and Dumas, Galle and Thompson, Todd A},
  issn         = {0004-637X},
  journal      = {ASTROPHYSICAL JOURNAL},
  keywords     = {STAR-FORMATION LAW,(CO)-C-12 2-1 MAP,NEARBY GALAXIES,SPIRAL GALAXIES,MILKY-WAY,FORMATION EFFICIENCY,INTERSTELLAR-MEDIUM,DISK GALAXIES,GRAVITATIONAL STABILITY,SUPERCLOUD FORMATION,galaxies: individual (M51),galaxies: ISM,galaxies: star formation,ISM: kinematics and dynamics},
  language     = {eng},
  number       = {1},
  pages        = {22},
  title        = {Gas kinematics on giant molecular cloud scales in M51 with PAWS : cloud stabilization through dynamical pressure},
  url          = {http://dx.doi.org/10.1088/0004-637X/779/1/45},
  volume       = {779},
  year         = {2013},
}

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